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4 Link Suspension

Discussion in '40- & 55-Series Tech' started by FJ40cruiser, Jun 6, 2003.

  1. FJ40cruiser

    FJ40cruiser

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    I looked at " space ghosts junk" and wasa truly impressed. Could anyone shed some lite on this 4 link suspension for me. What is is composed of, pros/cons if any, ect. I've recently found a restorable 40 in a local junkyard. The 40 is going to get crushed fairly shortly, The frame and the cowl is in decent enough shape for me to make the perfect rockcrawler. If I were to start this project a suspension similiar to space ghosts would be a strongly desired option. I need some info and advice.
     
  2. woody

    woody Internet Fireman Staff Member

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    I saw some of the first pics of SG's suspension...and he and I discussed it even in 2002 when he was still in discussion stage.

    I have not taken a tape to it (yet!) but his seems to follow the general "75% rule" of design.

    rear: uppers are ~30", lowers are ~40"....upper is triangulated, lower is splayed slightly. I'm working with similar numbers but gonna 1/4 elliptical instead. Vertical separation at the axle is in the 9" range, about 7" at the frame. His roll center and Instant center seem pretty good, but he does get a bit of wheel hop on steep climbs....controllable tho.

    front: Y-type 4-link with a panhard. IMO, I'm not a fan, since on articulation it tends to want to "twist" the axle, but with the poly incorporated in there there is enuf give. I would have only Y'd side and left the other as a single lower for less resistance. It works well on flats and downhills, but tends to not flex as nice unloaded (uphills)

    Mike's uses all heims, and tho I haven't looked, I suspect they are all QA-1 joints, 5/8" diameter hole, 3/4" thread. Strong and durable. $30 each at Jegs....16 on his rig I believe = ~$500 in heims....hehehe

    The best reading source for suspension design is on pirate4x4.com...you can spend weeks there searching and learning, and there is always someone asking a question. locate the "god of suspension" thread - 20+ pages of information, some good, some crap, and start weeding those who know from those tho are full of it, and then follow their posts.

    I've been researching for over a year, and now have a bare/cleaned rear housing on the garage floor with a pair of leaf packs laying next to it ready to be chopped. Tossing in 4 links and hanging springs is the easy part...understanding the calculations and having a basic idea of WHY the suspension will work is the hard part. You don't need to know the exact numbers, but need to understand the relation between everything.
     
    BAJA FJ40 likes this.
  3. SpaceGhost

    SpaceGhost

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    What specific questions do you have?

    All the links, upper and lower are the same length. Coil overs are about $400 a wheel. Links and rod ends are gonna be another $600 - $800. Sway bar is about $300. The rear tires rubbed the frame under compression, cut it off behind the tub and tube it. Lots easier to fit everything. The tube work to support the suspension and tie it all to gether is important, but not rocket science.

    I did not design, or build it. I assisted the crew at Badlands Machine Shop. Time is money, they built and installed it in less than a week and I was wheeling it.
     
  4. woody

    woody Internet Fireman Staff Member

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    Yes, I need to bring a tape measure next weekend....and stop drooling long enuf to look! hehehe
     
  5. KMAN

    KMAN

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    And they don't have to do it twice :G